Filtering system and filtering method

Abstract

A filtering method includes the following steps: receiving an sound signal; decomposing the sound signal into a primary lung sound signal and a reference heart sound signal; adjusting the reference heart sound signal according to a weighted value to generate an adjusted heart sound signal; and subtracting the adjusted heart sound signal from the primary lung sound signal to generate a filtered lung sound signal.

What is claimed is: 
     
       1. A filtering system, comprising:
 an input and output interface, configured to receive an sound signal; and 
 an adaptive filtering device, configured to decompose the sound signal into a primary lung sound signal and a reference heart sound signal, adjust the reference heart sound signal according to a weighted value to generate an adjusted heart sound signal, and subtract the adjusted heart sound signal from the primary lung sound signal to generate a filtered lung sound signal; 
 wherein the adaptive filtering device further comprises:
 a bandpass filter, configured to filter the sound signal into a filtered signal of 20-300 hertz (Hz) as the reference heart sound signal; and 
 an adaptive filter, configured to generate the weighted value, and subtract the adjusted heart sound signal from the primary lung sound signal to output the filtered lung sound signal; 
 
 wherein a step size of the adaptive filter is less than 0.03. 
 
     
     
       2. The filtering system of  claim 1 ,
 wherein the filtered lung sound signal is fed back to the adaptive filter, and the adaptive filter generates an updated weighted value according to the weighted value and the filtered lung sound signal. 
 
     
     
       3. The filtering system of  claim 2 , wherein the step size of the adaptive filter is 0.006. 
     
     
       4. The filtering system of  claim 2 , wherein a window size of the adaptive filter is less than 256 audio points. 
     
     
       5. The filtering system of  claim 1 , wherein order of the bandpass filter is 2nd order or 4th order. 
     
     
       6. A filtering method, comprising:
 receiving an sound signal; 
 decomposing the sound signal into a primary lung sound signal and a reference heart sound signal; 
 adjusting the reference heart sound signal according to a weighted value to generate an adjusted heart sound signal, wherein the weighted value is generated by an adaptive filter, and a step size of the adaptive filter is less than 0.03; 
 subtracting the adjusted heart sound signal from the primary lung sound signal to generate a filtered lung sound signal; and 
 filtering the sound signal into a filtered signal of 20-300 hertz (Hz) as the reference heart sound signal. 
 
     
     
       7. The filtering method of  claim 6 , further comprising:
 generating the weighted value; 
 subtracting the adjusted heart sound signal from the primary lung sound signal to output the filtered lung sound signal; 
 feeding back the filtered lung sound signal to an adaptive filter; and 
 generating an updated weighted value according to the weighted value and the filtered lung sound signal.